Patent GB-1323164-A (GB)
Title: Digital data communication multiple line control
IPC: G06F13/22
Filed: 1970-09-08
Abstract: 1323164 Digital transmission; plurality of out stations BURROUGHS CORP 8 Sept 1970 [19 Sept 1969] 42860/70 Heading H4P An arrangement switching data between a processor and a plurality of separate channels operating at different bit rates and formats has a separate word for each channel circulated in turn from a register combined with a logic network which controls the switching functions sequentially on a time division basis at the highest one of a plurality of differing frequency clock pulses generated simultaneously within the arrangement, any one of which is selectable by a first portion of each control word when in the control register. The apparatus may be arranged to accommodate different types of both synchronous and asynchronous systems. A processor 10, which may be a computer is required to communicate in both directions with a number of remote stations 18, 20 on a time division basis, information being initially received in interface register 26 and transferred at appropriate time into a buffer register 28. A register 30 having, say, 16 storage positions, one for each channel, extracts control words singly and sequentially which are routed into registers 26, 28 under the control of clock counter 34. As a new word is transferred into register 28 the previous word is applied to a write bus through a logic circuit 36. A switching circuit 38, synchronized with 32 sequentially connects input and output lines of each adaptor 14, 16, &c. to registers 40, 42 respectively, the contents of 40 being applied to circuit 36 whereas register 42 is set by 36. A word stored in register 26 has four "fields" the first of which determines the state of the processor interface, e.g. idle or occupied; an adaptor address (AD) identifies one of the adaptors 14, 16; a data/control field (DC) stores data or control information for transfer between processor 10 and register 28; and a control field (CC) identifies various operations such as the path information in the (DC) field. A word storing register 28 contains six "fields" see Fig. 3 (not shown) two of which (C1 C2) store data characters (T) identifying the type of equipment in use, i.e. speed and format, and two for counting sequence and controlling timing operations. The remaining "field" (BI/BC) provides a number of control functions, i.e. "out of service", "look for ring indication", "initiate transmit" or "receive", &c.  All functions are synchronized with clock pulses CP from 34 so that transfer from processor 10 to register 26 takes place during one clock time and retransfer into register 28 in the next clock time. During a transit mode, on initiation by a (B1 = 2) signal, characters are transferred from (C2) into (C1) field through a translator (214) which modifies the character by adding start/ stop bits, parity bits, or other formats changes and then from the (C1) field serially into register 42 for transmission. Clock 34 operates as a binary divider, the four lowest order stages RTO-RT3 controlling scanning of line adaptors 14, 16, &c. and switching circuits 32, 38. Higher order stages RT4-RT25 are applied to a network (232) Fig. 9 (not shown). An RT4 output may change level once per scan, RT5 alternate scans, and RT6 every fourth scan, &c. By controlling the initial setting of the (BT) field and the rate, e.g. RT4 at which the (BT) field can be decremented to 0, the C1 shift rate may be controlled at integral multiples.  Bit rates which differ from integral multiples may be accommodated by increasing the division constant by 1, i.e. RT4 to RT5 for predetermined time intervals during the run of a character thus adjusting the total character time generated. This process is performed in both transmit and receive modes. In the latter mode, the translator (214) operates oppositely to the transmit mode, and may if necessary reverse the order of bits to place the most significant into proper position.